Fetal growth traits such as birth weight, fetal length, ponderal index and head circumference are significantly associated with short-term outcomes such as perinatal morbidity/mortality and long-term adverse health outcomes including obesity, diabetes, and cardiovascular and complications. Both genetic and non-genetic factors influence fetal growth. A clear understanding of the genetics and environmental factors that influence fetal growth will give insights into mechanisms underlying the associations between fetal growth and chronic disease in later life, and can point to early intervention targets. The Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD) Fetal Growth Studies found significant differences in fetal growth among four US ethnic groups. Other studies showed ethnic differences in rates of low birth weight and skinfold thickness. The basis for these ethnic differences is not clear. Therefore, a genetic approach to study the determinants of fetal growth and interactions between genetic and environmental factors is critical for elucidating mechanisms underlying the links between skeletal growth, birth weight and adult chronic diseases, and to gain new insights into genetic contributions to fetal growth differences among individuals and ethnicities, such as African American and Hispanic